JP2016071285A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of appropriately determining the state of a toner bottle whose toner therein is soon run out.SOLUTION: An image forming apparatus 1000 comprises: an image forming part including a developing unit 44 that develops an electrostatic latent image formed on a photoreceptor drum 40 on the basis of image data; a toner bottle 60 that replenishes the developing unit 44 with toner; a sensor 20 that detects the concentration of toner in the developing unit 44; a counter 66 that counts the number of pixels of an image formed by the image forming part; a unit replenishment amount calculation part 1106 that outputs a replenishment signal for driving the toner bottle 60 and replenishing the developing unit 44 with toner; an estimation part 1107 that estimates the concentration of toner in the developing unit 44 from the count value of the counter 66 and the replenishment signal; an estimation part 1108 that estimates the error in the toner replenishment amount according to the concentration of toner estimated and the concentration of toner corresponding to the measurement value of the sensor 20; and a determination part 1109 that determines the state in which toner is soon run out as replacement timing of the toner bottle 60 when the error in the toner replenishment amount is a threshold (A) or lower.SELECTED DRAWING: Figure 8

Description

  The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus including a determination unit that determines a replacement time of a toner bottle for supplying toner to a developing device.

  In an image forming apparatus such as a copier or a laser beam printer, bottle near-end determination is performed to determine a replacement time immediately before the toner bottle capacity is empty. Display to prompt.

  Conventionally, toner is supplied from a toner bottle to a developing device via a toner supply container called a hopper. The hopper is provided with a weighing sensor, and the toner replenishment amount error is calculated using the toner amount inside the hopper detected by the weighing sensor. The toner replenishment amount error is a difference between the nominal toner replenishment amount per pump and the actual toner replenishment amount. The bottle near end determination is performed based on the tendency that the toner replenishment amount error tends to increase toward the minus side toward the bottle near end.

  However, in recent years, with the cost reduction of the entire image forming apparatus, it has been required to perform bottle near-end determination without mounting a weighing sensor. Further, with the downsizing of image forming apparatuses, a configuration in which toner is directly supplied from a toner bottle to a developing device without having a hopper is widely adopted. Since an apparatus having no hopper does not have a weighing sensor provided in the hopper, it is necessary to estimate a toner replenishment amount error without using a toner amount measured by the weighing sensor and determine bottle near end. .

  As an image forming apparatus that estimates a toner replenishment amount error without using a weighing sensor, an image forming apparatus that uses a toner replenishment amount calculated from a pixel count number obtained from image information and a replenishment count is known. That is, when the change amount of the cumulative value of the toner replenishment amount with respect to the cumulative value of the pixel count number of the formed image is larger than the upper limit value, the toner replenishment amount is decreased, and when smaller than the lower limit value, the toner replenishment amount is increased. Thus, a technique for stabilizing the toner density has been proposed. An example of such a technique is Patent Document 1.

JP 2008-20695 A

  However, although the above-described conventional technique can estimate the tendency of the toner replenishment amount error in the toner bottle alone, the toner replenishment amount error that changes so that the toner replenishment amount error gradually increases toward the bottle end. Cannot be estimated. For this reason, there is a problem that the bottle near end of the toner bottle cannot be properly determined using the estimated toner replenishment amount error.

  The present invention estimates the developer replenishment amount error that gradually increases toward the minus side toward the replacement timing of the developer replenishing means, and can appropriately determine the replacement timing of the developer replenishing means. An object is to provide a forming apparatus.

  In order to solve the above problems, an image forming apparatus according to the present invention includes an image carrier, an exposure unit that exposes the image carrier based on image data to form an electrostatic latent image, and the electrostatic latent image. An image forming unit including a developing unit that supplies the developer to the image and develops; a replenishing unit that replenishes the developer with the developer; a density measuring unit that measures a developer density in the developing unit; and the image A counting unit that counts the number of pixels of an image formed by the forming unit; and an output unit that outputs a drive command signal to the driving unit that drives the replenishing unit and replenishes the developing unit with the developer filled in the replenishing unit. First estimating means for estimating the developer concentration of the developing means using the count value of the counting means and the drive command signal, the developer concentration estimated by the first estimating means, and the density Measured by measuring means A second estimating means for estimating an error in the amount of developer replenished from the replenishing means using the image density; and the replenishing means when the developer replenishing amount error falls below a predetermined threshold (A). And determining means for determining that the replacement time has come.

  The present invention provides a developer consumption amount obtained from a count value of a counting unit that counts the number of pixels of a formed image, and a developer replenishment amount obtained from a drive command signal of a drive unit that replenishes the developer with the developer. From this difference, the developer concentration of the developing means is estimated. Further, a developer replenishment amount error is estimated from the difference between the estimated developer concentration and the measured value of the density measuring unit, and when the estimated developer replenishment amount error becomes equal to or greater than a predetermined value (A), the replenishment unit It is determined that it is time for replacement. As a result, it is possible to estimate the developer replenishment amount error that gradually increases toward the minus side toward the replacement timing of the developer replenishing means, and to appropriately determine the replacement timing of the developer replenishing means.

1 is a diagram illustrating a schematic configuration of an image forming apparatus to which the present invention is applied. FIG. 2 is a cross-sectional view illustrating a schematic configuration of a developing device in the image forming apparatus of FIG. 1. FIG. 2 is a waveform diagram for explaining a method of counting density information of an image information signal in the image forming apparatus of FIG. FIG. 2 is a block diagram illustrating a configuration of a toner replenishment control controller in the image forming apparatus of FIG. 1. 6 is a flowchart illustrating a procedure of toner supply processing. 3 is a block diagram illustrating a configuration of a toner supply control controller of the image forming apparatus according to the embodiment. FIG. It is a flowchart which shows the procedure of a bottle near end determination process. It is a flowchart which shows the procedure of the 1st bottle near end determination process of step S304 of FIG. It is a flowchart which shows the procedure of the 2nd bottle near end determination process of step S305 of FIG. It is a figure for demonstrating the effect of a prior art. It is a figure for demonstrating the effect of embodiment. FIG. 10 is a block diagram of a toner replenishment control controller in a modification of the embodiment.

  Hereinafter, embodiments will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus to which the present invention is applied. This image forming apparatus is an electrophotographic digital copier. However, the present invention is not limited to this, and can be equally applied to an electrophotographic system, an electrostatic recording system, and other various image forming apparatuses. That is, in the present invention, for example, a latent image corresponding to an image information signal is formed on an image bearing member such as a photosensitive member or a dielectric member by an electrophotographic method or an electrostatic recording method, and the formed latent image is developed. The present invention can be widely applied to an image forming apparatus having a configuration in which a visible image is transferred to a transfer material and fixed.

  In FIG. 1, an image forming apparatus 1000 includes an image forming unit as a hardware configuration. The image forming unit includes a photosensitive drum 40 as an image carrier, and a static eliminator 41, a primary charger 42, a developer 44, a cleaner 50, and a surface of the photosensitive drum 40 that are arranged to face the photosensitive drum 40. The exposure part which forms is provided. The exposure unit includes a semiconductor laser 36 as a light source, a rotating polygon mirror 37, an f / θ lens 38, and a fixed mirror 39. The exposure unit exposes the photosensitive drum 40 based on the image data of the document 31 read by the image sensor 33 through the lens 32 to form an electrostatic latent image corresponding to the document 31.

  The developing device 44 includes a toner supply tank 60 for supplying toner 63 as a developer to the developing device 44. The toner replenishing tank 60 is a toner bottle and includes a conveying screw 62, a motor 70 for driving the conveying screw 62, and a gear train 71.

  FIG. 2 is a cross-sectional view showing a schematic configuration of a developing device in the image forming apparatus of FIG.

  In FIG. 2, the developing device 44 is disposed to face the photosensitive drum 40, and the inside thereof is divided into a first chamber (developing chamber) 52 and a second chamber (stirring chamber) 53 by a partition wall 51 extending in the vertical direction. It is divided into and. A nonmagnetic developing sleeve 54 that rotates in the direction of the arrow is disposed in the developing chamber 52, and a magnet 55 is fixedly disposed in the developing sleeve 54. The developing sleeve 54 carries and conveys a two-component developer whose layer thickness is regulated by a blade 56, and develops an electrostatic latent image by supplying non-magnetic toner particles to the photosensitive drum 40 in a developing area facing the photosensitive drum 40. To do. The two-component developer includes magnetic carrier particles and non-magnetic toner particles (hereinafter simply referred to as “toner”), and the electrostatic latent image is developed with toner. In order to improve the developing efficiency, that is, the toner application rate to the electrostatic latent image, a developing bias voltage obtained by superimposing a DC voltage on an AC voltage is applied to the developing sleeve 54 from a power source 57.

  In the developing chamber 52 and the stirring chamber 53, stirring screws 58 and 59 are arranged, respectively. The stirring screw 58 stirs and conveys the developer in the developing chamber 52. The agitating screw 59 agitates and conveys the toner 63 supplied by the rotation of the conveying screw 62 from the toner discharge port 61 of the toner replenishing tank 60 and the two-component developer 43 already contained in the developing device 44. Uniform toner density. The partition wall 51 is formed with a developer passage (not shown) that allows the developing chamber 52 and the stirring chamber 53 to communicate with each other at the front and back end portions in FIG. Then, the developer in the developing chamber 52 in which the toner is consumed due to the development and the toner concentration is reduced by the conveying force of the stirring screws 58 and 59 through the one developer passage is transferred from the developing chamber 52 to the stirring chamber 53. Move to. Further, the developer whose toner concentration has been recovered in the stirring chamber 53 moves from the stirring chamber 53 into the developing chamber 52 through the other developer passage.

  The image forming apparatus 1000 also includes a transfer material carrying belt 47 supported by support rollers 45 and 46 below the photosensitive drum 40. A transfer charger 49 is provided at a position facing the photosensitive drum 40 with the transfer material carrying belt 47 interposed therebetween.

  In the image forming apparatus having such a configuration, the image of the document 31 to be copied is projected onto the image sensor 33 such as a CCD by the lens 32. The image sensor 33 decomposes the image of the document 31 into a large number of pixels and generates a photoelectric conversion signal corresponding to the density of each pixel. The analog image signal output from the image sensor 33 is sent to the image signal processing circuit 34, where each pixel is converted into a pixel image signal having an output level corresponding to the density of the pixel, and the pulse width modulation circuit 35 is converted. Sent to. The pulse width modulation circuit 35 forms and outputs a laser driving pulse having a width (time length) corresponding to the level of each input pixel image signal.

  FIG. 3 is a waveform diagram for explaining a method of counting the density information of the image information signal in the image forming apparatus of FIG. 1, and FIG. 3 (a) corresponds to the level of the input pixel image signal. 4 is a diagram showing a laser driving pulse formed by a pulse width modulation circuit 35. FIG. As shown in FIG. 3A, a wider driving pulse W is applied to a high density pixel image signal, and a narrower driving pulse S is applied to a low density pixel image signal. A drive pulse I having an intermediate width is formed for each pixel image signal.

  The laser drive pulse output from the pulse width modulation circuit 35 is supplied to a semiconductor laser 36 which is a latent image forming unit, and causes the semiconductor laser 36 to emit light for a time corresponding to the pulse width. Accordingly, the semiconductor laser 36 is driven for a longer time with respect to the high density pixel and is driven with a shorter time for the low density pixel. Therefore, the photosensitive drum 40 is exposed in a long range in the main scanning direction for high density pixels, and is exposed in a short range in the main scanning direction for low density pixels. That is, the dot size of the electrostatic latent image is different according to the pixel density. FIG. 3D is a diagram showing an electrostatic latent image corresponding to the laser driving pulse of FIG. In FIG. 3D, the toner consumption in the electrostatic latent images L, M, and H of low density, medium density, and high density pixels is naturally higher in the case of high density pixels than in the case of low density pixels. Will also increase.

  Laser light 36a emitted from the semiconductor laser 36 is swept by a rotating polygon mirror 37, and is spot-imaged on the photosensitive drum 40 by an f / θ lens 38 and a fixed mirror 39 that directs the laser light 36a toward the photosensitive drum 40. . In this way, the laser beam 36a scans the photosensitive drum 40 in a direction (main scanning direction) substantially parallel to the rotation axis of the photosensitive drum 40, and forms an electrostatic latent image on the surface thereof. The latent image forming means may be a light source such as an LED array in addition to the semiconductor laser 36, and is not particularly limited.

  The photosensitive drum 40 is an electrophotographic photosensitive drum having amorphous silicon, selenium, OPC, etc. on its surface and rotating in the direction of the arrow. After being uniformly discharged by the charge eliminator 41, the photosensitive drum 40 is uniformly charged by the primary charger 42. The Thereafter, as described above, exposure scanning is performed with the laser beam modulated in accordance with the image data, and an electrostatic latent image corresponding to the image data is formed. The electrostatic latent image is reversely developed by a developing device 44 as developing means, and a visible image (toner image) is formed. The reversal development is a development method in which a toner charged with the same polarity as that of the latent image is attached to a region exposed to light of a photoconductor to visualize the toner. The toner image on the photosensitive drum 40 is transferred to the transfer material 48 held on the transfer material carrying belt 47 by the action of the transfer charger 49.

  In the image forming apparatus 1000 of FIG. 1, only one image forming station (including the photosensitive drum 40, the charge eliminator 41, the primary charger 42, the developing device 44, etc.) is illustrated for the sake of simplicity. . However, when the image forming apparatus is a color image forming apparatus, for example, four image forming stations for cyan, magenta, yellow, and black colors sequentially arranged on the transfer material carrying belt 47 along the moving direction thereof. Have Then, an electrostatic latent image for each color obtained by color-separating the image of the original on the photosensitive drum of each image forming station is sequentially formed, developed by a developing device having the corresponding color toner, and held by the transfer material carrying belt 47. Then, the images are sequentially transferred onto the transferred transfer material 48.

  The transfer material 48 to which the toner image has been transferred is separated from the transfer material carrying belt 47 and conveyed to a fixing device (not shown), where the toner image is fixed to the transfer material 48. Residual toner remaining on the photosensitive drum 40 after the transfer is removed by the cleaner 50.

  When the toner in the developing device 44 is consumed in connection with such an image forming process, toner corresponding to the amount of toner consumption is supplied from the toner supply tank 60 filled with toner to the developing device 44.

  An inductance sensor 20 as a toner concentration measuring unit is installed on the bottom wall of the developing chamber 52 of the developing device 44, and a detection value corresponding to an actual toner concentration of the developer 43 in the developing chamber 52 is controlled by a CPU 67 described later. Output to the replenishment control controller 1100. Further, the image forming apparatus 1000 is provided with a pixel count type counter 66 which is a consumed toner calculation unit, and the level of the output signal of the image signal processing circuit 34 is counted for each pixel.

  That is, the output signal of the pulse width modulation circuit 35 is supplied to one input of the AND gate 64, and a clock pulse as shown in FIG. 3B is supplied from the clock pulse oscillator 65 to the other input of the AND gate. Is done. Therefore, the number of clock pulses corresponding to the pulse widths of the laser drive pulses S, I, and W as shown in FIG. 3C from the AND gate 64, that is, the number of clocks corresponding to the density of each pixel. A pulse is output. The number of clock pulses is accumulated by the counter 66 for each image, and the pixel count number is calculated. For example, the maximum pixel count for A4 paper is 3707 × 106. The pulse integration signal C1 for each image in the counter 66 corresponds to the amount of toner consumed from the developing device 44 in order to form one toner image of the document 31. There are various types of pixel counters 66 such as a method of counting the number of pixels directly from image data in addition to the one synchronized with the laser driving pulse described above.

  In the developing device 44, the toner replenishment amount is determined based on the output of the inductance sensor 20 and the pixel count number of the pixel counter 66, and the motor drive circuit 69 of the motor 70, which is toner replenishment means, is driven and controlled for each image formation. The At this time, if the replenishment amount is large, the driving time of the motor 70 is longer, and if the replenishment amount is small, the driving time of the motor 70 is shorter. The driving force of the motor 70 is transmitted to the conveying screw 62 via the gear train 71, and the conveying screw 62 conveys the toner 63 in the toner replenishing tank 60 and replenishes the developing device 44 with a predetermined amount of toner.

  Hereinafter, the toner supply process in the image forming apparatus of FIG. 1 will be described in detail with reference to the drawings.

  FIG. 4 is a block diagram showing the configuration of the toner replenishment control controller in the image forming apparatus of FIG. In FIG. 4, the toner supply controller 1100 has a CPU 67 and a storage unit 68. Further, the replenishment control controller 1100 includes a first replenishment amount determination unit 1101 and a difference calculation unit 1102. The first supply amount determination unit 1101 receives the pixel count number from the counter 66. The difference calculation unit 1102 calculates the difference between the toner concentration in the developing chamber 52 detected by the inductance sensor 20 and the toner concentration target value determined by the toner concentration target value determination unit 1103. The toner replenishment control controller 1100 also includes a second replenishment amount determination unit 1104, a replenishment amount summation unit 1105, and a unit replenishment amount calculation unit 1106. The unit replenishment amount calculation unit 1106 calculates a unit replenishment amount and outputs a correction drive command to the motor drive circuit 69.

  Hereinafter, specific toner supply processing will be described.

  FIG. 5 is a flowchart illustrating a procedure of toner replenishment processing. The toner supply process is executed by the CPU 67 of the toner supply controller 1100 of the image forming apparatus 1000 according to a toner supply process program stored in a ROM (not shown). When the image forming process is started by the image forming apparatus 1000, the toner is consumed, and the toner supply process is started as the toner is consumed.

  In FIG. 5, when the toner replenishment process is started, the CPU 67 controls the first replenishment amount determination unit 1101 to receive the pixel count number from the counter 66 which is a consumed toner calculation unit (step S201). Next, the CPU 67 controls the first supply amount determining unit 1101 to determine a first toner supply amount corresponding to the toner amount consumed by the developing device 44 based on the input pixel count number (step S202). ). At this time, the first replenishment amount determination unit 1101 determines the first toner replenishment amount using a conversion table indicating the input pixel count number and the correspondence relationship between the pixel count number and the toner replenishment time created in advance. To do.

  Next, the CPU 67 controls the difference calculation unit 1102 to receive an output value corresponding to the toner density in the developing device 44 from the inductance sensor 20 (step S203). Next, the CPU controls the difference calculation unit 1102 to convert the output value of the inductance sensor 20 into the toner density value in the developing device 44, and the obtained toner density value and the toner density target value determination unit 1103 determine it. A difference from the target value is calculated (step S204). The toner density target value is determined by the toner density target value determination unit 1103 based on the environment and other conditions.

  Next, the CPU 67 controls the second replenishment amount determination unit 1104 to sum the difference obtained by the difference calculation unit 1102 by a predetermined gain, and the difference accumulated value obtained up to the previous time by the predetermined gain. Is determined as the second toner supply amount (step S205). The second supply amount determination unit 1104 calculates the accumulated difference between the measured value of the toner density in the developing device 44 calculated in step S204 and the target value.

  Next, the CPU 67 controls the replenishment amount summation unit 1105 to obtain the sum of the first toner replenishment amount and the second toner replenishment amount and set it as the total replenishment amount (step S206). Next, the CPU 67 determines whether or not the obtained total replenishment amount is negative (step S207). As a result of the determination in step S207, when the total replenishment amount is not negative but positive (“NO” in step S207), the toner replenishment operation is performed, and the CPU 67 controls the second replenishment amount determination unit 1104, The current difference is added to the previous accumulated difference value (step S209). This prepares for the toner supply process from the next time onward.

  After adding the current difference to the accumulated difference value (step S209), the CPU 67 controls the unit supply amount calculation unit 1106 to supply the total supply amount obtained by the supply amount addition unit 1105 to the replenishment in the unit supply amount calculation unit 1106. It adds to the quantity buffer value (step S210). The replenishment amount buffer value is an accumulation of the replenishment amount received by the unit replenishment amount calculation unit 1106 from the replenishment amount summation unit 1105. As will be described later, the unit replenishment amount buffer value is a unit replenishment amount that is a predetermined value. When it exceeds, toner replenishment is executed.

  After adding the total replenishment amount to the replenishment amount buffer value (step S210), the CPU 67 determines whether or not the replenishment amount buffer value has reached a predetermined unit replenishment amount, that is, the replenishment amount buffer value is equal to or greater than the unit replenishment amount. It is determined whether or not (step S211). As a result of the determination in step S211, if the replenishment amount buffer value is equal to or greater than the unit replenishment amount (“YES” in step S211), the CPU 67 instructs the motor drive circuit 69 to rotate the motor 70 as toner replenishing means. A drive command signal is output (step S212). The motor drive circuit 69 drives the replenishment motor 70 and replenishes a unit replenishment amount of toner from the toner bottle 60 to the stirring chamber of the developing device 44 every time a drive command signal is input.

  After outputting the drive command signal to the motor drive circuit 69, the CPU 67 subtracts the unit supply amount from the supply amount buffer value (step S213), and returns the process to step S211. That is, the CPU 67 repeats the processes in steps S211 to 213 until the supply amount buffer value falls below the unit supply amount. If the result of determination in step S211 is that the replenishment amount buffer value is below the unit replenishment amount (“NO” in step S211), the CPU 67 ends the replenishment operation while retaining the replenishment buffer value for the next time.

  On the other hand, if the total replenishment amount is negative as a result of the determination in step S207 (“YES” in step S207), the toner replenishment amount is reduced. Therefore, the CPU 67 controls the second supply amount determining unit 1104 to not add the current difference to the accumulated difference value up to the previous time, and keep the value up to the previous time (step S208). Advances to step S210.

  According to the processing of FIG. 5, the toner consumption amount is obtained based on the pixel count number, and the first toner supply amount is determined from the obtained toner consumption amount. Further, an actual measured value of the toner density in the developing device 44 is obtained based on the output of the inductance sensor 20, and the second supply amount is determined based on the obtained actual measured value and the target value. Then, when the combined supply amount of the first correction amount and the second correction amount reaches a predetermined unit supply amount, toner supply from the toner bottle is executed. Thereby, the toner density in the developing chamber 52 of the developing device 44 can be maintained at a predetermined value or more.

  Hereinafter, bottle near-end determination processing for determining the replacement time of the toner bottle using the image forming apparatus according to the embodiment will be described.

  FIG. 6 is a block diagram illustrating a configuration of the toner supply control controller of the image forming apparatus according to the embodiment. In FIG. 6, the toner replenishment control controller 1200 is different from the toner replenishment control controller 1100 of FIG. 4 in that a toner density estimation unit 1107, a toner replenishment amount error estimation unit 1108, and a forced replenishment determination unit 1110 are provided. . The toner replenishment control controller 1200 also includes the toner replenishment control controller of FIG. 4 in that the first and second bottle near-end determination units 1109 and 1111 are provided, and the total bottle near-end determination unit 1112 and the bottle replacement display unit 1113 are provided. Is different.

  Hereinafter, the bottle near end determination process executed by the CPU 167 of the toner replenishment control controller 1200 of FIG. 6 will be described.

  FIG. 7 is a flowchart showing the procedure of the bottle near end determination process. This bottle near-end determination process is executed by the CPU 167 of the toner replenishment control controller 1200 of FIG. 6 according to a bottle near-end determination process program stored in a ROM (not shown). Note that the processing in FIG. 7 is repeatedly executed, for example, every 0.1 second.

  In FIG. 7, when the image forming apparatus 1000 is turned on (on), bottle near-end determination processing starts. When the bottle near end determination process is started, the CPU 167 first calls each previous delay calculation variable from the storage unit 68 (step S301). This is because the current bottle near-end determination process is executed following the bottle near-end determination process.

  Next, the CPU 167 determines whether or not the power of the image forming apparatus 1000 is turned off (step S302). If the power is not turned off (“NO” in step S302), the CPU 167 performs the first bottle near end determination in the first bottle near end determination unit 1109 (step S304). After performing the first bottle near-end determination, the CPU 167 performs the second bottle near-end determination in the second bottle near-end determination unit 1111 (step S305). Next, the CPU 167 determines in the general bottle near end determination unit 1112 whether the bottle near end has been determined by the first bottle near end determination or the bottle near end has been determined by the second bottle near end determination (step S306).

  As a result of the determination in step S306, if the bottle near-end is determined by the first or second bottle near-end determination (“YES” in step S306), the CPU 167 displays an instruction to replace the bottle on the bottle replacement display unit 1113. (Step S307). Next, the CPU 167 determines whether or not the toner bottle has been replaced, and waits until it is replaced (step S308). If the result of the determination in step S308 is that the bottle has been replaced (“YES” in step S308), the CPU 167 returns the process to step S302 and repeats the above process until the image forming apparatus 1000 is powered off.

  If the image forming apparatus 1000 is turned off as a result of the determination in step S302 (“YES” in step S302), the CPU 167 stores each state quantity value in the storage unit 68 (step S303), and performs this processing. Exit.

  According to the process of FIG. 7, when the near end of the toner bottle is determined by the first or second bottle near end determination, and it is determined that the bottle is near the end, a bottle replacement instruction is displayed. Thus, it is possible to appropriately determine the bottle near end of the toner bottle and instruct the user to replace it with a new toner bottle.

  Next, the first bottle near-end determination process in step S304 of FIG. 7 will be described.

  FIG. 8 is a flowchart showing the procedure of the first bottle near-end determination process in step S304 of FIG. The first bottle near-end determination process is executed by the CPU 167 of the toner replenishment control controller 1200 in FIG. 6 according to a first bottle near-end determination process program stored in a ROM (not shown). The first bottle near-end determination process is repeatedly executed, for example, every 0.1 seconds while the image forming process is being executed.

  In FIG. 8, when the first bottle near-end determination process is started, the CPU 167 controls the toner density estimation unit 1107 to receive the pixel count number from the counter 66 (step S401). Further, the CPU 167 controls the toner density estimation unit 1107 to receive a toner supply signal from the unit supply amount calculation unit 1106 (step S402). The toner replenishment signal is a signal transmitted to the motor drive circuit 69, and is turned on and off in pulses every time the motor drive circuit 69 (see FIG. 1) is instructed to replenish one pump of toner from the toner bottle 60. This is a drive command signal.

  Next, the CPU 167 controls the toner density estimation unit 1107 to estimate the toner density as the developer density in the developing device 44 based on the pixel count number and the toner supply signal (step S403). The pixel count number corresponds to the amount of toner consumed. Therefore, the consumed toner amount can be obtained from the pixel count number based on the consumed toner amount per unit pixel count value. On the other hand, the toner replenishment signal corresponds to the amount of toner to be replenished. That is, the toner bottle has a nominal toner replenishment amount per drive of the replenishment pump for each type, and the replenished toner amount can be obtained from the toner replenishment signal based on the nominal value.

  Therefore, the toner density in the developing device 44 can be estimated from the difference between the toner consumption amount obtained from the pixel count number and the toner replenishment amount obtained from the toner replenishment signal. When the toner replenishment amount is larger than the toner consumption amount, the toner concentration inside the developing device 44 increases. When the toner supply amount is small relative to the toner consumption amount, the toner concentration inside the developing device 44 decreases. To do.

  After estimating the toner concentration in the developing device 44 (step S403), the CPU 167 controls the toner replenishment amount error estimating unit 1108 to calculate the estimated toner concentration and the toner concentration corresponding to the sensor output value of the inductance sensor 20. Is calculated (step S404). The inductance sensor 20 is a sensor that outputs a measurement value corresponding to the actual toner density in the developing device 44. Therefore, the difference obtained in step S404 corresponds to the difference between the estimated value of the toner density in the developing device 44 and the actually measured value.

  Next, the CPU 167 controls the toner replenishment amount error estimation unit 1108 to estimate the toner replenishment amount error from the difference between the estimated value of the toner density and the actual measurement value (step S405).

  The toner replenishment amount error is defined as follows. That is, the toner concentration estimation unit 1107 uses the nominal toner replenishment amount per pump as the reference toner replenishment amount when calculating the replenished toner amount. However, in an actual toner bottle, the amount of toner replenishment for each pump varies. As a specific index representing the variation in the toner replenishment amount, the ratio of the actual toner replenishment amount to the nominal toner replenishment amount per pump is used. This ratio is defined as a toner replenishment amount error (developer replenishment amount error).

  The toner replenishment amount error is 0 when the nominal toner replenishment amount is equal to the actual toner replenishment amount, a negative value when the actual toner replenishment amount is less than the nominal toner replenishment amount, and a positive value when it is greater. Incidentally, the difference between the estimated value of the toner density and the actually measured value described above is caused by a toner replenishment amount error of the toner bottle. Therefore, the toner replenishment amount error can be estimated based on the difference between the estimated toner concentration and the actually measured toner concentration and the number of times of driving the pump for replenishing the toner with respect to the toner consumption amount obtained from the pixel count number. As the absolute value of the difference between the estimated value of the toner density and the actual measurement value increases, the absolute value of the toner replenishment amount error also increases.

  After estimating the toner supply amount error (step S405), the CPU 167 controls the first bottle near-end determination unit 1109 using the estimated toner supply amount error to determine the near-end of the toner bottle.

  When the toner replenishing amount error is a small value on the minus side, it means that the toner replenishing amount per pump is smaller than the nominal value. As the toner bottle approaches the bottle near end, the toner capacity in the toner bottle decreases, so the toner replenishment amount per pump gradually decreases. Thus, the bottle near-end determination is performed using the characteristic that the toner replenishment amount decreases.

  Specifically, the CPU 167 first determines whether the toner supply signal is on (step S406). This is because the toner bottle approaches the near end with the toner supply process. As a result of the determination in step S406, if the toner replenishment signal is ON (“YES” in step S406), the CPU 167 determines whether or not the toner replenishment amount error estimated in step S405 is equal to or less than a predetermined threshold (A) set in advance. Is determined (step S407). This is because if the toner replenishment amount error is equal to or less than the predetermined threshold value (A), it can be determined that the toner bottle is approaching the bottle near end. The threshold value (A) may be appropriately determined by experiments or the like.

  As a result of the determination in step S407, if the toner replenishment amount error is equal to or smaller than the predetermined threshold (“YES” in step S407), the CPU 167 increments the first bottle near-end determination count value C1 (step S409). This is to obtain the frequency at which the determination result for determining the bottle near end is output.

  Next, the CPU 167 determines whether or not the first bottle near-end determination count value C1 has reached a preset threshold value (B), that is, whether or not the threshold value (B) is exceeded (step S410). If the result of determination in step S410 is that the first bottle near-end determination count value C1 is greater than or equal to a preset threshold value (B) (“YES” in step S410), the CPU 167 determines that the toner bottle is near-end. (Step S411), this process is terminated. The threshold value (B) may be appropriately determined by experiments or the like.

  On the other hand, if the result of determination in step S406 is that the toner replenishment signal is not on (“NO” in step S406), the CPU 167 ends this process. This is because if the toner is not replenished, the toner bottle does not become near end, and it is not necessary to execute bottle near end determination. If the result of determination in step S407 is that the toner replenishment amount error is larger than the predetermined threshold (A) (“NO” in step S407), the CPU 167 resets the first bottle near-end determination counter value (step S408). ), This process is terminated. This is because if the toner supply amount error is larger than the predetermined threshold (A), it cannot be said that the bottle near end of the toner bottle is close.

  On the other hand, if the result of determination in step 410 is that the first bottle near-end determination count value C1 is not greater than or equal to the preset threshold value (B) (“NO” in step S410), the CPU 167 determines that the bottle near-end is not determined. The process ends. This is because it is not necessary to replace the toner bottle 60 if the count value C1 is smaller than the threshold value (B).

  According to the processing of FIG. 8, the toner density in the developing device 44 is estimated based on the pixel count number and the toner replenishment signal (step S403), and the actual density obtained from the estimated toner density and the output value of the inductance sensor 20 is obtained. The difference from the toner density is calculated (step S404). Further, the toner replenishment amount error is estimated based on this difference (step S405). When the toner supply amount error becomes equal to or less than the predetermined threshold value (A) and the frequency at which the toner supply amount error becomes equal to or less than the predetermined threshold value (A) becomes equal to or higher than the predetermined threshold value (B), the bottle near end is determined. Therefore, the bottle near end of the toner bottle can be properly determined.

  Next, the second bottle near-end determination process in step S305 in FIG. 7 will be described.

  FIG. 9 is a flowchart showing the procedure of the second bottle near-end determination process in step S305 of FIG. The CPU 167 of the toner replenishment control controller 1200 in FIG. 6 executes the second bottle near-end determination process according to a second bottle near-end determination process program stored in a ROM (not shown). The second bottle near-end determination process is repeatedly executed, for example, every 0.1 second while the image forming process is being executed.

  In FIG. 9, when the second bottle near-end determination process is started, the CPU 167 receives a detected value of the toner density in the developing device 44 corresponding to the sensor output value from the inductance sensor 20 (step S501). Next, the CPU 167 controls the forced supply determination unit 1110 to receive a supply amount buffer value from the unit supply amount calculation unit 1106 (step S502). Next, the CPU 167 determines whether or not the current image forming mode is the forced supply mode (step S503). The forced supply mode is a mode in which toner supply is performed in a state where new image formation in the image forming unit is interrupted and toner consumption associated with image formation is stopped. When the toner concentration in the developing device 44 corresponding to the measurement result of the inductance sensor 20 is equal to or less than a predetermined threshold (C), the amount of toner to be replenished is small relative to the amount of toner consumed, and thus the developing device 44 indicates that the toner density in 44 is decreasing. Therefore, it is necessary to interrupt the new image formation and replenish the toner. The threshold value (C) may be appropriately determined by experiments or the like.

  Even when the replenishment amount buffer value is equal to or greater than the predetermined threshold (D), the toner replenishment amount by the replenishment motor 70 does not catch up with the toner consumption amount, and the replenishment amount buffer value obtained by toner replenishment control continues to accumulate. is there. For this reason, even when the replenishment amount buffer value (total amount of developer replenishment amount) is equal to or greater than the predetermined threshold (D), it is necessary to temporarily replenish the toner and perform toner replenishment. Specifically, the replenishment motor 70 has a hardware limitation, and there is a limitation on the number of times the toner can be replenished per unit time. For example, when images with a high toner density are continuously formed, the total amount of toner replenishment in the replenishment amount summation unit 1105 increases with a momentum exceeding the restriction on the number of replenishment times, and the total replenishment amount value is displayed in the unit replenishment amount computation unit 1106. The supply amount buffer value continues to accumulate and exceeds the threshold (D). As described above, when the replenishment amount buffer value exceeds the threshold value (D), the new image formation is temporarily interrupted so that a new pixel count is not input, and then the replenishment motor 70 is driven to replenish the toner. To do. As a result, the replenishment amount buffer value in the unit replenishment amount calculation unit 1106 can be subtracted to recover the state where the toner replenishment amount of the replenishment motor 70 catches up with the toner consumption amount. The threshold value (D) may be appropriately determined by experiments or the like.

  If the result of determination in step S503 is not the forced supply mode (“NO” in step S503), the CPU 167 controls the forced supply determination unit 1110 to make the following determination. That is, the CPU 167 determines whether the toner density in the developing device 44 corresponding to the output value of the inductance sensor 20 is equal to or lower than a predetermined threshold (C), or whether the replenishment amount buffer value is equal to or higher than the predetermined threshold (D) (step). S504). As a result of the determination in step S504, when the toner density is equal to or lower than the predetermined threshold (C) or the replenishment amount buffer value is equal to or higher than the predetermined threshold (D), the CPU 167 shifts the processing to the forced replenishment mode (step S505). .

  After shifting to the forced supply mode, or when the result of determination in step S503 is that the forced supply mode is in effect (“YES” in step S503), the CPU 167 advances the process to step S506. That is, the CPU 167 determines whether or not the toner concentration in the developing device 44 corresponding to the output value of the inductance sensor 20 is equal to or higher than a predetermined threshold (C) and the replenishment amount buffer value is returned to a predetermined threshold (D) or lower. Is determined (step S506). This is because if the toner density is equal to or higher than the predetermined threshold (C) and the supply amount buffer value is equal to or lower than the predetermined threshold (D), the bottle near end is not suspected. As a result of the determination in step S506, if the condition is not satisfied even if the developer toner is supplied more than a predetermined number of times (“NO” in step S506), bottle near end is suspected. Therefore, the CPU 167 performs the bottle near end determination in the second bottle near end determination unit 1111 (steps S509 to S514).

  Here, if the toner bottle is not in the bottle near-end state and the toner replenishment amount per pump is close to the nominal value, the toner corresponding to the output value of the inductance sensor 20 can be obtained by supplying toner of a predetermined number of pumps in the forced replenishment mode. Concentration and replenishment buffer values are restored. However, when the toner bottle approaches the near end and the toner replenishment amount per pump decreases, the total amount of toner replenishment amount is small even when toner of a predetermined number of pumps is replenished. For this reason, the toner concentration corresponding to the output value of the inductance sensor 20 and the supply amount buffer value are not recovered. Accordingly, if the toner concentration corresponding to the output value of the inductance sensor 20 and the replenishment amount buffer value are not recovered even when toner is replenished by a predetermined number of pumps or more in the forced replenishment mode, it can be determined that the bottle near end is reached. What is necessary is just to determine suitably the number of pumps for determining with a bottle near end by experiment etc.

  Returning to FIG. 9, the CPU 167 first determines whether or not the toner replenishment signal is ON in the specific second bottle near-end determination (step S <b> 509). This is because if the toner supply process is not executed, the toner bottle will not become near-end. As a result of the determination in step S509, if the toner supply signal is ON (“YES” in step S509), the CPU 167 counts up the second bottle near-end determination count value C2 (step S510).

  Next, the CPU 167 determines whether or not the toner density in the developing device 44 corresponding to the output value of the inductance sensor 20 is equal to or higher than a predetermined threshold (C) (step S511). If the result of determination in step S511 is not greater than or equal to the predetermined threshold (C) (“NO” in step S511), whether the second bottle near-end determination count value C2 has reached the predetermined threshold, that is, the predetermined threshold (E) It is determined whether or not this is the case (step S513). If the result of determination in step S513 is greater than or equal to a predetermined threshold (E) (“YES” in step S513), the CPU 167 determines that the toner bottle is bottle near-end (step S514), and ends this processing. The threshold value (E) may be appropriately determined by experiments or the like.

  On the other hand, if the result of determination in step S504 is negative (“NO” in step S504), the CPU 167 ends this process. This is because the possibility of a bottle near end is low. If it is determined in step S506 that the toner density is equal to or higher than the threshold value (C) and the replenishment amount buffer value is equal to or lower than the threshold value (D) (“YES” in step S506), the CPU 167 determines the second bottle near end. The count value C2 is reset (step S507). This is because the possibility of a bottle near end is low. Next, the CPU 167 releases the forced supply mode (step S508), and ends this process.

  If the result of determination in step S509 is that the toner supply signal is not on (“NO” in step S509), the CPU 167 ends this processing. This is because if the toner is not replenished, the toner bottle does not become near end, and it is not necessary to execute bottle near end determination.

  If the determination in step S511 indicates that the toner concentration in the developing device 44 corresponding to the output value of the inductance sensor 20 is equal to or greater than the predetermined threshold (C) (“YES” in step S511), the CPU 167 performs processing. Proceed to step S512. That is, the CPU 167 once resets the second bottle near-end determination count value C2 (step S512), and ends this process. This is because the possibility of a bottle near end is low.

  According to the processing of FIG. 9, when the toner density in the developing device 44 corresponding to the detection value of the inductance sensor 20 is equal to or less than a predetermined threshold (C), or the replenishment amount buffer value is equal to or greater than the predetermined threshold (D). Then, toner supply is performed in a state where the new image formation is interrupted and the toner consumption is stopped. This toner supply mode is called a forced supply mode. If the measured value of the inductance sensor 20 does not recover after shifting to the forced supply mode, it is determined that the bottle near the end of the toner bottle. Thereby, it is possible to appropriately determine the bottle near end in the forced supply mode.

  In the present embodiment, as the bottle near end determination, only the first bottle near end determination in FIG. 8 may be executed without using the second bottle near end determination in FIG. 9. This also makes it possible to make an appropriate bottle near-end determination.

  In the present exemplary embodiment, the driving amount or driving time of the replenishing motor 70 that supplies the toner in the toner bottle 60 to the developing device 44 may be controlled based on the toner replenishing amount error estimated by the toner replenishing amount error estimating unit 1108. it can.

  Hereinafter, the effects of the present embodiment will be described in comparison with the effects of the prior art.

  First, the effect of the prior art will be described with reference to FIG.

  FIG. 10 is a diagram for explaining the effect of the prior art. Specifically, FIG. 10A is a diagram showing an actual measured value of an error in toner replenishment amount for an arbitrary toner bottle (N = 1) from the start of use in a new state to the end of use after the bottle is empty. FIG. 6B is a diagram illustrating an estimated value of a toner replenishment amount error estimated by the conventional technique. In FIGS. 11A and 11B, the horizontal axis represents the total number of times the replenishment pump is driven (total number of replenishments), and the vertical axis represents the toner replenishment amount error.

  In FIG. 11A, the toner replenishment amount error changes from the beginning of using the toner bottle in a new state to the vicinity of the point P1, and changes with the toner replenishment amount error of about 0 as the center while fluctuating in a long cycle. I understand that The fluctuation in the long period is due to the influence of the surrounding environment where the image forming apparatus main body is placed. If the temperature and humidity fluctuate in a long period depending on the season, it is considered that the bottle replenishment amount error is also affected. On the other hand, from around the point P1, the toner replenishment amount error gradually decreases, and the toner bottle is finally emptied to reach the bottle end.

  In the prior art, the toner replenishment amount error is estimated based on a change amount of the cumulative value of the toner replenishment amount with respect to the cumulative value of the pixel count number obtained from the image information. Specifically, the pixel count number from the start of use of the toner bottle to the estimation time of the toner supply amount error and the cumulative value of the toner supply amount are calculated. The toner replenishment amount is measured by counting the number of replenishments by the replenishment motor 70. A change amount of the toner replenishment amount is calculated using the cumulative value of the toner replenishment amount with respect to the cumulative value of the pixel count from the start of bottle use to the present time, and a toner replenishment amount error is estimated using the change amount. Then, the toner density is stabilized by increasing or decreasing the toner supply amount according to the estimated toner supply amount error.

  Such a conventional technique uses a pixel count number from the initial stage of a toner bottle to the time of estimation of a replenishment amount error and a change amount of a cumulative value of the toner replenishment amount. An indicator of whether there is a large or small error is obtained.

  The estimation result of the toner replenishment amount error in the conventional technique is as shown in FIG. In FIG. 10B, the average toner replenishment amount error can be estimated up to the point P1 except for the long period fluctuation, but the toner replenishment amount error gradually decreases toward the bottle end after the point P1. The characteristics cannot be estimated. Therefore, in such a conventional technique, the bottle near-end determination cannot be properly performed using the estimated toner replenishment amount error.

  On the other hand, FIG. 11 is a figure for demonstrating the effect of the above-mentioned embodiment.

  The toner replenishment amount error estimated in the above embodiment is shown in FIG. Note that FIG. 11A is a diagram showing an actual measurement value of the toner replenishment amount error of the toner bottle (N = 1), as in FIG. 10A.

  As shown in FIG. 11 (b), in the present embodiment, it follows the long-period fluctuation up to the point P1, and. The total replenishment frequency (horizontal axis) can also follow the characteristic that the toner replenishment amount error gradually decreases toward the bottle end after the point P1. In the present embodiment, the toner supply amount error is estimated by comparing the successively estimated toner concentration with the actual toner concentration detected by the inductance sensor 20. Therefore, it is possible to follow the decrease in the toner replenishment amount error that appears characteristically only after the point P1. In this way, an estimated value of the toner replenishment amount error corresponding to the actually measured value of the toner density in the developing device 44 is obtained, and the bottle near end determination is performed using the estimated toner replenishment amount error. Judgment is possible.

  Next, another specific effect of the embodiment in which the first bottle near-end determination unit and the second bottle near-end determination unit are executed will be described.

  The second bottle near-end determination unit 1111 uses the feature that when the bottle near-end is reached, the toner replenishment amount decreases, and the toner density in the developing device 44 corresponding to the detection value of the inductance sensor 20 decreases. That is, when the medium-high density image is continuously passed, the toner replenishment amount consumed is larger than the reduced toner replenishment amount. Therefore, the inductance sensor 20 is not delayed so much from the decrease in the toner replenishment amount error after the point P1. The toner density corresponding to the detected value also decreases. For this reason, a bottle near end can be determined by the 2nd bottle near end determination part.

  On the other hand, when a low density image is continuously fed, the amount of toner replenishment consumed is small relative to the amount of toner replenishment that decreases after the point P1, so even if the toner replenishment amount error starts to decrease after the point P1, the inductance sensor The toner density corresponding to the detected value of 20 does not decrease easily. For this reason, the timing which can determine with a bottle near end will become late only by 2nd bottle near end determination. In particular, since there are many cases in which low density images are continuously passed through an image forming apparatus for office use, near-end determination that can cope with continuous passing of low density images is required.

  Further, since the second bottle near-end determination is based on the criterion that the toner concentration corresponding to the detection value of the inductance sensor 20 is equal to or less than a predetermined threshold, the bottle near-end determination cannot be performed unless the toner concentration is deviated. However, a state where the toner density deviates from the target value causes an image density shift. Therefore, it is desirable to perform bottle near-end determination in a state where the toner density does not deviate from the target value.

  On the other hand, since the first bottle near-end determination unit uses the estimated toner supply amount error, the first bottle near-end determination unit directly monitors a decrease in the toner supply amount from the toner bottle. Therefore, the bottle near end determination can be performed at a suitable timing regardless of the density of the image to be passed. Further, the bottle near-end determination can be performed even if the toner concentration corresponding to the detection value of the inductance sensor 20 does not become a predetermined threshold value or less, that is, the toner concentration does not deviate.

  As described above, in the present embodiment in which the first bottle near-end determination and the second bottle near-end determination are used in combination, the bottle near-end determination of the toner bottle can be suitably performed.

  Hereinafter, toner replenishment control in a modification of the above embodiment will be described in detail with reference to the drawings. In this modification, the toner replenishment amount error estimated by the toner replenishment amount error estimation unit 1108 is applied to toner replenishment control.

  FIG. 12 is a block diagram of a toner replenishment control controller in a modification of the above embodiment. In FIG. 12, the toner replenishment control controller 1300 differs from the toner replenishment control controller 1200 of FIG. 6 mainly in the following points. That is, FIG. 12 shows that the toner replenishment amount error estimated by the toner replenishment amount error estimation unit 1108 is introduced into the replenishment amount summation unit 1105 as the third replenishment amount determined by the third replenishment amount determination unit 1114. Different from FIG.

  In the above embodiment, the replenishment amount summation unit 1105 determines the sum of the replenishment amount by inputting the pixel count corresponding to the consumed toner amount and the output value of the inductance sensor 20 corresponding to the toner density in the developing device 44. Toner replenishment control was performed. Therefore, the toner replenishment amount error corresponding to the replenished toner amount is not taken into account in the toner replenishment control. However, the toner density in the developing device 44 is affected by the ratio of the replenished toner amount to the consumed toner amount. For this reason, by calculating the sum of the replenishment amount in consideration of the estimated value of the toner replenishment amount error as well as the input, it is possible to realize toner replenishment control that takes into account variations in the amount of toner to be replenished.

  That is, using the toner supply amount error estimated by the toner supply amount error estimation unit 1108, the third supply amount determination unit 1114 determines a third toner supply amount that takes into account variations in the toner supply amount. Then, in the replenishment amount summation unit 1105, the total replenishment amount obtained by adding the three replenishment amounts determined by the first replenishment amount determination unit 1101, the second replenishment amount determination unit 1104, and the third replenishment amount determination unit 1114. Is output to the unit supply amount calculation unit 1106. Thus, more realistic toner replenishment control can be realized by adjusting the drive amount or drive time of the replenishment motor 70 in consideration of variations in the amount of toner to be replenished.

20 Inductance sensor 36 Semiconductor laser 40 Photosensitive drum 44 Developer 60 Toner supply tank 66 Pixel counter 67 CPU
69 Motor drive circuit 70 Supply motor

Claims (8)

Image forming apparatus comprising: an image carrier; an exposure unit that exposes the image carrier based on image data to form an electrostatic latent image; and a developing unit that supplies developer to the electrostatic latent image and develops the image. And
Replenishing means for replenishing developer to the developing means;
Density measuring means for measuring the developer density in the developing means;
Counting means for counting the number of pixels of an image formed by the image forming unit;
An output means for driving the replenishing means to output a drive command signal to a driving means for replenishing the developing means with the developer filled in the replenishing means;
First estimating means for estimating the developer concentration of the developing means using the count value of the counting means and the drive command signal;
Second estimating means for estimating a developer replenishment amount error from the replenishing means using the developer concentration estimated by the first estimating means and the developer concentration measured by the density measuring means;
A determination unit that determines that the supply unit has reached the replacement time when the developer supply amount error is equal to or less than a predetermined threshold (A);
An image forming apparatus comprising:   2. The image forming apparatus according to claim 1, wherein the developer replenishment amount error is a ratio of an actual developer replenishment amount to a nominal developer replenishment amount per drive of the driving unit.   The determination unit determines that the supply unit has reached a replacement time when the frequency at which the developer supply amount error is equal to or less than a predetermined threshold (A) is equal to or greater than a predetermined threshold (B). The image forming apparatus according to claim 1.   4. The image forming apparatus according to claim 1, wherein the replenishing unit is a bottle filled with the developer, and the determination unit determines a bottle near end of the bottle. 5. .   When the developer concentration measured by the density measuring unit is equal to or less than a predetermined threshold (C), or the total amount of developer replenishment amount corresponding to the drive command signal is equal to or greater than a predetermined threshold (D), When the developer replenishment is started in a state where new image formation in the image forming unit is stopped, and the developer concentration and the total amount of developer replenishment are not restored even if the developer is replenished after a predetermined number of times, 5. The image forming apparatus according to claim 1, further comprising a second determination unit that determines that the replenishment unit has reached a replacement time. 6.   6. The image forming apparatus according to claim 5, further comprising an interrupting unit that interrupts a replenishment mode in which developer replenishment is performed in a state where the new image formation is stopped when the developer concentration and the developer replenishment amount are restored. apparatus.   The image forming apparatus according to claim 1, further comprising a control unit that controls a driving amount or a driving time of the driving unit in accordance with the developer replenishment amount error.   8. The developer housed in the developing means is a two-component developer containing toner particles and carrier particles, and the replenishing means replenishes the toner particles to the developing means. The image forming apparatus according to any one of the above.